6 Things Omega-3s Can Do For Your Health—And 3 Things They Can't

Anyone who has ever burped her way through a bottle of fish oil supplements has probably wondered to herself, "Is this really worth it?!"

While the fishy aftertaste can certainly be unpleasant, those oils (technically, omega-3 fatty acids—docosahexaenoic acid [DHA] and eicosapentaenoic acid [EPA], to be specific) are thought to have inflammation-fighting and heart-protecting benefits. So at first blush, you're likely to answer your own question with a hearty yes.

But fish oil research has been consistently... inconsistent. In fact, there are conflicting viewpoints for nearly every rumored benefit of those omega-3s. For starters, it seems that getting omega-3 fatty acids through our diets is an entirely different beast than taking omega-3 fatty acids in supplement form. "In general, consuming omega-3s from fish seems to have a number of health benefits, but taking omega-3 supplements might not have the same effects," says Paul M. Coates, PhD, director of the Office of Dietary Supplements (ODS) at the National Institutes of Health. Researchers don't entirely understand why that's the case, he says. To try to capitalize on the benefits of fish, though, the particular types of omega-3s in seafood, DHA and EPA, have landed in your supplements. They're thought to have a stronger connection to good health than the varieties found in plant-based foods like soybean oil and flaxseed.

There are still a bunch of questions to be answered by ongoing omega-3 research. In the meantime, here's what the latest science says omega-3s can—and can't—do for your health. (Want to pick up some healthier habits? Sign up to get daily healthy living tips and more delivered straight to your inbox!)

Omega-3 fatty acids probably can't save your memory.
Supplements, at least, don't seem to do the trick. One of the largest and longest studies of omega-3 pills found no brain benefits among 4,000 patients, with an average age of 72, who supplemented for 5 years.

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Katie Black Photography/Getty Images

Some research has suggested brain benefits in animals, says study author Emily Chew, MD, deputy clinical director at the National Eye Institute at the NIH. But "very few studies have demonstrated a positive or protective effect of omega-3 fatty acids to improve cognition" in humans, she says. In her study, a daily dose of 1,000 mg for 5 years didn't do anyone any memory favors (it also didn't prove to be harmful, either). It's possible, she says, that a higher dose could still be helpful or that getting omega-3s from our diets would make more of a difference to our brains. "Perhaps there are other ingredients that are more important in protecting our brain than the omega-3s, or it might be a combination of ingredients in fish that are important," she says.

They can probably fight off some inflammation.
Quick refresher: There are two kinds of inflammation. One is acute and crops up when your body is fighting an illness, healing a sprained ankle, or coughing through an asthma attack. The other is the chronic, low-grade kind that you might not even notice but that quietly ups your risk for serious health concerns like heart disease, diabetes, and arthritis. Omega-3s, in the diet and from supplements, seem to have an impact on both types of inflammation, says Philip Calder, PhD, a professor of nutritional immunology at the University of Southampton in the UK.

The best-understood theory for how omega-3s dampen that inflammation has to do with what you're not getting if you're getting more omega-3s. Omega-6 fatty acids, much more plentiful in the typical American diet from our vegetable oil intake, are converted in the body into inflammation-causing chemicals, Calder says. If we ate more omega-3-rich foods or relied on a large enough dose of the supplements, there simply wouldn't be as many omega-6s around to produce inflammation.

Omega-3s may also produce their very own chemicals that "turn off" inflammation, Calder says, by destroying or decreasing the activity of inflammatory chemicals and cells.

They might also help joint pain.
There's "reasonably robust" evidence that omega-3s can do a number on pain, Calder says, although exactly when, where, and how remain a bit mysterious. We know that omega-3 supplements seem to help people with rheumatoid arthritis, an autoimmune disorder that damages the lining of the joints. With fish oil, RA patients are able to take fewer anti-inflammatory meds, Coates says, "but [supplements] don't have consistent effects on the amount of pain and tenderness in the joints themselves." In other words, omega-3s probably aren't a replacement for traditional treatment, but they might deliver a 1-2 punch alongside it. And for some unexplained reason, omega-3s don't seem to help much at all for osteoarthritis pain.

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Cristina Pedrazzini/Getty Images

Researchers aren't giving up on fish oil's pain-fighting properties, though. There's early work being done to examine the impact fish oil could have on headache duration and severity, Calder says. The problem is, most of the studies are still done either in test tubes or in mice. It's tough, therefore, to figure out dosage and delivery to real-live humans, he says.

They can probably protect you from heart disease, but they might not save your life.
The whole omega-3 craze can be traced back to heart health, Calder says. Danish researchers originally ID'ed the fatty acids as a major player in the otherwise-not-too-healthy diet of native Greenlanders. They rarely ate fruits and veggies—you know, because of all that ice up there—but they had surprisingly low rates of heart disease. What they did eat in abundance was fish, whale, and seal. Maybe, the researchers hypothesized, it was the omega-3s in all that fatty seafood saving their tickers. Fast forward a bit, and we now know that even among Western populations, people who eat fish are at lower risk of heart disease than people who don't, plain and simple. What's more, the more fish we eat, the more we're protected from heart disease risk factors like high blood pressure and high cholesterol, Calder says.

Until about 2010, it also seemed that people at high risk for cardiovascular events, like a heart attack or a stroke, were more likely to survive them if they'd popped omega-3 supplements. But more recent research has had difficulty replicating those results, Calder says. "That has obviously rocked the boat." Taking fish oil, it now seems, won't stave off strokes or heart attacks, even though eating more fish still seems to protect people at average risk from ever developing heart problems to begin with. The supplements do lower triglyceride levels, a type of fat in the blood, so if yours are high, he recommends discussing supplementation with your doctor.

They can probably improve your mood.
It's not totally clear how they work on our emotions, Coates says, but because there are high amounts of omega-3s and other fatty acids in the membranes of our brain cells, getting enough might affect the way those cells function. That, in turn, "could influence the manifestation of depression," he says. So far, the results have been varied, both by the type of mental health concern—mild vs. major depression vs. bipolar disorder, for example—and the type and amount of omega-3. A recent review of 26 studies found a small benefit of taking omega-3s over a placebo in reducing depression symptoms, and even some suggestion that they might work as well as antidepressants, but don't go breaking up with your therapist quite yet. "Overall, research suggests that omega-3s might be helpful for reducing symptoms of depression in some people, but they aren't a substitute for and shouldn't be taken in place of conventional treatments for depression," Coates says.

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They can't stop you from getting cancer.
Don't get carried away by promising studies in animals that would have you believe omega-3 fatty acids work miracles against cancer. "I think omega-3s stop rats and mice from getting colorectal cancer in laboratories, but that's different from people with a genetic predisposition and lifelong exposure to carcinogens," Calder says. "I don't think the science is strong enough."

Because inflammation seems to fuel the growth of cancer cells, it's reasonable enough to imagine that inflammation-fighting omega-3s would in turn fight cancer's spread, Coates says. The fatty acids have been linked to a reduced risk of breast and colorectal cancers in animal studies, but researchers haven't totally figured out why. Plus, conflicting studies have suggested both an increase and a decrease in prostate cancer risk after taking omega-3 supplements. The Office of Dietary Supplements is cosponsoring an upcoming clinical trial on omega-3s for cancer, Coates says, but with so little evidence and no consistent pattern at the moment, he can't currently recommend taking them for cancer prevention.

They can definitely help you have a healthy baby.
Fish oil's biggest and best-understood role in human health is actually in early brain and visual development, Calder says. Because of this crucial link, women are uniquely suited to convert the simplest forms of omega-3 fatty acids, the ones that come from plant sources, into the more health-bolstering varieties. "Women are actually much better than men at synthesizing their own omega-3s," Calder says, because the fats are so important to fetal development (bragging rights!). We even have special chemical transporters that usher those omega-3s across the placenta to the fetal side, he says.

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Jose Luis Pelaez Inc/Getty Images

We don't really know if they can help your asthma.
Those native Greenlanders and other people who traditionally eat a fish-heavy diet also have low rates of asthma, so some researchers have wondered whether omega-3 fatty acids might once again be at play. While their anti-inflammatory effects could help quiet the immune response complicit in an asthma attack, some studies have found an effect, while others have found nothing. Upcoming research cosponsored by the Office of Dietary Supplements should help us understand a lot more about asthma, obesity, and omega-3s, Coates says.

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Tom Merton/Getty Images

They might help you lose weight.
While eating fish can help people maintain a healthy weight, the idea that omega-3s might actually help you shed pounds is a new one. Recent research published in the journal Scientific Reports suggests that fish oil encourages dormant fat cells to convert to a more active state in which they can be burned for energy. For the study, Japanese researchers fed one group of mice a diet high in omega-3 fish oils; another group ate a similar high-fat diet—but with no omega-3s. After 16 weeks, the mice eating fish oil had 15-25% less fat on their frames, compared with the non-fish-oil group. More important, certain fat cells in the omega-3 mice had undergone a dramatic change: They could convert from inert white fat cells (the kind of fat that accumulates on your thighs, hips, and belly) into active, calorie-burning beige fat. We're born with plenty of brown and beige cells, but we tend to lose them as we age—it's one of the reasons metabolism slows as we get older, say the researchers. Omega-3s from fish appear to help replace these metabolically active fat cells, they say.

What YOU can do is start eating more fish.
"Anyone who is genuinely interested in their health and well-being should do that," Calder says. Just make sure it's the fatty kind, like salmon, tuna, sardines, and herring (but steer clear of some other types of fish). Of course, there's a time and place for supplements—"Supplements are an alternative for people who can't or don't eat fish," he says—but it certainly sounds like there's nothing quite like the real thing. At the very least, neither should hurt. "I don't think there would be any harm from either eating more fish or taking omega-3 supplements," he says. "I think there's good potential for benefits of omega-3s and low likelihood of risk."

If you don't take supplements and you don't do fish, you're probably still getting about 100 mg of omega-3s a day, since there are low levels in a handful of other foods. One meal of a lean, white fish like tilapia delivers about 300 mg, while a good portion of fatty fish like salmon will give you more like 1,500 to 2,500. "That's one reason why fish is so important to a healthy diet," Calder says, "but of course, people don't eat that sort of fish every day." A normal fish oil supplement packs about 300 mg, while a concentrated version might have more like 450 to 800, he says. "In other words, to match what you get from having a nice salmon or tuna meal, you would need to be taking three or four capsules of a highly concentrated supplement," he says.

Aim for about 8 to 12 ounces of seafood each week, Coates says, with an emphasis on the fatty stuff. That'll also provide you with a bounty of other goodies, including selenium, zinc, iodine, and protein. "Eating fish has a number of health benefits in addition to supplying omega-3s," he says, "so it certainly makes sense for people to incorporate seafood into their diets."

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